Edit: See the answer below.
I finally give up and come here to ask you for my problem...
I'm using a UIScrollView for a scrolling menus with little icons.
On each page, with paging enabled, there's an icon in the center, and 2 and a half other visible icons on the left and right. I can move from one icon to its neighbour, and that is fine, but the point is that if I do a fast scrolling, it will not move from more than 3 icons, which is the width of the screen.
What I would want is to be able to scroll on more than 3 icons, and that the magnet behaviour is only triggered when it's slowing down.
I've tried to schedule the scroll view to calculate its velocity, and set the pagingEnabled attribute to NO when it's moving fast and YES again when it's slowing down, but as soon as it is set to YES, the view comes back very fast at its original position, as if it was not detecting that I had brought it to a new page. Would anyone know why it does this? And if I have a way to tell the view "ok, now the paging is enabled but look, you're 15 pages later. Just center on the current page, don't come back at the beginning."
Here's my update function (if it can help):
-(void)update:(ccTime)dt
{
float velocity = fabsf((self.previousOffset-self.scrollView.contentOffset.y)/dt);
self.previousOffset = self.scrollView.contentOffset.y;
CCLOG(#"Velocity: %f", velocity);
if(self.scrollView.pagingEnabled)
{
if(velocity > 100)
{
self.scrollView.pagingEnabled = NO;
}
}
else
{
if(velocity < 100)
{
self.scrollView.pagingEnabled = YES;
}
}
}
I finally found a solution, which was pretty obvious, but that I did not see at the beginning, by using setContentOffset on the scrollView.
Here is the new update function:
-(void)update:(ccTime)dt
{
float velocity = 1000;
if(self.previousOffset)
{
velocity = fabsf((self.previousOffset-self.scrollView.contentOffset.y)/dt);
}
self.previousOffset = self.scrollView.contentOffset.y;
if(velocity < 300)
{
CGSize screenSize = [[CCDirector sharedDirector] winSize];
float halfScreen = screenSize.width/2;
CCLayer *panel = (CCLayer *)[self getChildByTag:1];
SQScrollViewMenu *menu = (SQScrollViewMenu *)[panel getChildByTag:1];
SQMissionItem *currentItem = (SQMissionItem *)[menu getChildByTag:currentPage];
float contentOffsetY = [self.scrollView contentOffset].y;
CCLOG(#"Currentpage: %i ; currentoffsetY: %f", currentPage, contentOffsetY);
float distance = contentOffsetY + [currentItem position].x - halfScreen + panel.position.x + menu.position.x + panel.parent.position.x - 60;
CCLOG(#"Which gives a distance of: %f", distance);
[self.scrollView setContentOffset:CGPointMake(0, distance) animated:YES];
self.previousOffset = 0;
[self unschedule:#selector(update:)];
CCLOG(#"Is unscheduled");
}
}
And it is almost working... at least, it is on simulator. But as soon as I try it on my iPhone 4, it does not work anymore. It always go into that update function, but 7 times among 8, it just blocks the scrollView as it is and does not drags it back to the position I give it... but sometimes it does.
Would anyone have an idea? I found similar issues on the net, but none of them could resolve this...
Related
My app is simple: I want to move a small uiimageview around a view of an iPad with the accelerometer (now Core Motion). So, I can move the uiimageview around with the accelerometer, but I am having trouble establishing working borders in landscape mode. So, here is my code. The problem is that the uiimageview tends to stick to the borders and some of the borders are not perfectly on the edge of the view. Here is my code, any help is greatly appreciated:
- (void)startMyMotionDetect
{
__block float stepMoveFactor = 15;
[self.motionManager
startAccelerometerUpdatesToQueue:[[NSOperationQueue alloc] init]
withHandler:^(CMAccelerometerData *data, NSError *error)
{
dispatch_async(dispatch_get_main_queue(),
^{
CGRect rect = self.sumbarine.frame;
float movetoY = rect.origin.x + (data.acceleration.x * stepMoveFactor);
float maxY = self.view.frame.size.width-rect.size.width;
float movetoX = (rect.origin.y + rect.size.height)
- (data.acceleration.y * stepMoveFactor);
float maxX = self.view.frame.size.height;
if ( movetoX >0 && movetoX < maxX ) {
rect.origin.x += (data.acceleration.y * stepMoveFactor);
};
if ( movetoY > 0 && movetoY < maxY ) {
rect.origin.y += (data.acceleration.x * stepMoveFactor);
};
[UIView animateWithDuration:0 delay:0
options:UIViewAnimationOptionCurveEaseIn
animations:
^{
self.sumbarine.frame = rect;
}
completion:nil
];
}
);
}
];
}
The sticking issue comes from your conditions for moving. Right now, you say, if "moveToX/Y" is > 0, and less than the width/height, then add Acceleration X/Y.
What happens if origin is == or >greater than "maxX/Y"? Answer: Nothing. And thus, the submarine image acts like it's stuck to a board. Probably it can move on the alternate axis, until it's finally stuck at a condition where it no longer can move.
You'll want to play around with your conditional rules. I do not know what type of actions/input you're trying to implement for gameplay, so I can't tell you what to do next. I'm assuming the sub is supposed to go up/down depending on some user gesture/action.
One last piece of advice. Accelerometers are based on G-Force... What this means for you is even though acceleration on some axis is positive when you move say left... There's also an inverse curve when you need apply the force needed to stop. Try looking at the motiongraphs app (available in documentation) to help you get a better feel/sense of this stuff.
And remember, have fun!
I have a UICollectionView with 6 pages, and paging enabled, and a UIPageControl. What I want is, when I came to the last page, if I drag to right, UICollectionView reloads from first page seamlessly.
- (void)scrollViewDidEndDecelerating:(UIScrollView *)sender
{
// The key is repositioning without animation
if (collectionView.contentOffset.x == 0) {
// user is scrolling to the left from image 1 to image 10.
// reposition offset to show image 10 that is on the right in the scroll view
[collectionView scrollRectToVisible:CGRectMake(collectionView.frame.size.width*(pageControl.currentPage-1),0,collectionView.frame.size.width,collectionView.frame.size.height) animated:NO];
}
else if (collectionView.contentOffset.x == 1600) {
// user is scrolling to the right from image 10 to image 1.
// reposition offset to show image 1 that is on the left in the scroll view
[collectionView scrollRectToVisible:CGRectMake(0,0,collectionView.frame.size.width,collectionView.frame.size.height) animated:NO];
}
pageControlUsed = NO;
}
It doesn't work like I want. What can I do?
Here's what I ended up with for my UICollectionView (horizontal scrolling like the UIPickerView):
#implementation UIInfiniteCollectionView
- (void) recenterIfNecessary {
CGPoint currentOffset = [self contentOffset];
CGFloat contentWidth = [self contentSize].width;
// don't just snap to center, since this might be done in the middle of a drag and not aligned. Make sure we account for that offset
CGFloat offset = kCenterOffset - currentOffset.x;
int delta = -round(offset / kCellSize);
CGFloat shift = (offset + delta * kCellSize);
offset += shift;
CGFloat distanceFromCenter = fabs(offset);
// don't always recenter, just if we get too far from the center. Eliza recommends a quarter of the content width
if (distanceFromCenter > (contentWidth / 4.0)) {
self.contentOffset = CGPointMake(kCenterOffset, currentOffset.y);
// move subviews back to make it appear to stay still
for (UIView *subview in self.subviews) {
CGPoint center = subview.center;
center.x += offset;
subview.center = center;
}
// add the offset to the index (unless offset is 0, in which case we'll assume this is the first launch and not a mid-scroll)
if (currentOffset.x > 0) {
int delta = -round(offset / kCellSize);
// MODEL UPDATE GOES HERE
}
}
}
- (void) layoutSubviews { // called at every frame of scrolling
[super layoutSubviews];
[self recenterIfNecessary];
}
#end
Hope this helps someone.
I've been using the Street Scroller sample to create an infinite scroller for images. That works fine until I wanted to set pagingEnabled = YES; Tried tweaking around the recenterIfNecessary code and finally realized that it's the contentOffset.x that has to match the frame of the subview that i want visible when paging stops. This really isn't going to work in recenterIfNecessary since you have no way of knowing it will get called from layoutSubviews. If you do get it adjusted right, the subview may pop out from under your finger. I do the adjustment in scrollViewDidEndDecelerating. So far I haven't had problems with scrolling fast. It will work and simulate paging even when pagingEnabled is NO, but it looks more natural with YES.
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
[super scrollViewDidEndDecelerating:scrollView];
CGPoint currentOffset = [self contentOffset];
// find the subview that is the closest to the currentOffset.
CGFloat closestOriginX = 999999;
UIView *closestView = nil;
for (UIView *v in self.visibleImageViews) {
CGPoint origin = [self.imageContainerView convertPoint:v.frame.origin toView:self];
CGFloat distanceToCurrentOffset = fabs(currentOffset.x - origin.x);
if (distanceToCurrentOffset <= closestOriginX) {
closestView = v;
closestOriginX = distanceToCurrentOffset;
}
}
// found the closest view, now find the correct offset
CGPoint origin = [self.imageContainerView convertPoint:closestView.frame.origin toView:self];
CGPoint center = [self.imageContainerView convertPoint:closestView.center toView:self];
CGFloat offsetX = currentOffset.x - origin.x;
// adjust the centers of the subviews
[UIView animateWithDuration:0.1 animations:^{
for (UIView *v in self.visibleImageViews) {
v.center = [self convertPoint:CGPointMake(v.center.x+offsetX, center.y) toView:self.imageContainerView];
}
}];
}
I have not used UICollectionView for infinite scrolling, but when doing it with a UIScrollView you first adjust your content offset (instead of using scrollRectToVisible) to the location you want. Then, you loop through each subview in your scroller and adjust their coordinates either to the right or left based on the direction the user was scrolling. Finally, if either end is beyond the bounds you want them to be, move them to the far other end. Their is a very good WWDC video from apple about how to do infinite scrolling you can find here: http://developer.apple.com/videos/wwdc/2012/
Typically, the scrollView's content view is a rectangle. But I would like to implement that is not a rectangle.... For example....
The yellow, Grid 6 is the current position...Here is the example flow:
User swipe to left. (cannot scroll to left) Current: 6.
User swipe to right. (scroll to right) Current: 7.
User swipe to down. (scroll to down) Current: 8.
User swipe to down. (cannot scroll to down) Current: 8.
As you can see, the Content view of the scrollView is not rectangle. Any ideas on how to implement it? Thanks.
This is an interesting idea to implement. I can think of a few approaches that might work. I tried out one, and you can find my implementation in my github repository here. Download it and try it out for yourself.
My approach is to use a normal UIScrollView, and constrain its contentOffset in the delegate's scrollViewDidScroll: method (and a few other delegate methods).
Preliminaries
First, we're going to need a constant for the page size:
static const CGSize kPageSize = { 200, 300 };
And we're going to need a data structure to hold the current x/y position in the grid of pages:
typedef struct {
int x;
int y;
} MapPosition;
We need to declare that our view controller conforms to the UIScrollViewDelegate protocol:
#interface ViewController () <UIScrollViewDelegate>
#end
And we're going to need instance variables to hold the grid (map) of pages, the current position in that grid, and the scroll view:
#implementation ViewController {
NSArray *map_;
MapPosition mapPosition_;
UIScrollView *scrollView_;
}
Initializing the map
My map is just an array of arrays, with a string name for each accessible page and [NSNull null] at inaccessible grid positions. I'll initialize the map from my view controller's init method:
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
[self initMap];
}
return self;
}
- (void)initMap {
NSNull *null = [NSNull null];
map_ = #[
#[ #"1", null, #"2"],
#[ #"3", #"4", #"5" ],
#[ null, #"6", #"7" ],
#[ null, null, #"8" ],
];
mapPosition_ = (MapPosition){ 0, 0 };
}
Setting up the view hierarchy
My view hierarchy will look like this:
top-level view (gray background)
scroll view (transparent background)
content view (tan background)
page 1 view (white with a shadow)
page 2 view (white with a shadow)
page 3 view (white with a shadow)
etc.
Normally I'd set up some of my views in a xib, but since it's hard to show xibs in a stackoverflow answer, I'll do it all in code. So in my loadView method, I first set up a “content view” that will live inside the scroll view. The content view will contain a subviews for each page:
- (void)loadView {
UIView *contentView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, [map_[0] count] * kPageSize.width, map_.count * kPageSize.height)];
contentView.backgroundColor = [UIColor colorWithHue:0.1 saturation:0.1 brightness:0.9 alpha:1];
[self addPageViewsToContentView:contentView];
Then I'll create my scroll view:
scrollView_ = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, kPageSize.width, kPageSize.height)];
scrollView_.delegate = self;
scrollView_.bounces = NO;
scrollView_.autoresizingMask = (UIViewAutoresizingFlexibleLeftMargin
| UIViewAutoresizingFlexibleRightMargin
| UIViewAutoresizingFlexibleTopMargin
| UIViewAutoresizingFlexibleBottomMargin);
I add the content view as a subview of the scroll view and set up the scroll view's content size and offset:
scrollView_.contentSize = contentView.frame.size;
[scrollView_ addSubview:contentView];
scrollView_.contentOffset = [self contentOffsetForCurrentMapPosition];
Finally, I create my top-level view and give it the scroll view as a subview:
UIView *myView = [[UIView alloc] initWithFrame:scrollView_.frame];
[myView addSubview:scrollView_];
myView.backgroundColor = [UIColor colorWithWhite:0.95 alpha:1];
self.view = myView;
}
Here's how I compute the scroll view's content offset for the current map position, and for any map position:
- (CGPoint)contentOffsetForCurrentMapPosition {
return [self contentOffsetForMapPosition:mapPosition_];
}
- (CGPoint)contentOffsetForMapPosition:(MapPosition)position {
return CGPointMake(position.x * kPageSize.width, position.y * kPageSize.height);
}
To create subviews of the content view for each accessible page, I loop over the map:
- (void)addPageViewsToContentView:(UIView *)contentView {
for (int y = 0, yMax = map_.count; y < yMax; ++y) {
NSArray *mapRow = map_[y];
for (int x = 0, xMax = mapRow.count; x < xMax; ++x) {
id page = mapRow[x];
if (![page isKindOfClass:[NSNull class]]) {
[self addPageViewForPage:page x:x y:y toContentView:contentView];
}
}
}
}
And here's how I create each page view:
- (void)addPageViewForPage:(NSString *)page x:(int)x y:(int)y toContentView:(UIView *)contentView {
UILabel *label = [[UILabel alloc] initWithFrame:CGRectInset(CGRectMake(x * kPageSize.width, y * kPageSize.height, kPageSize.width, kPageSize.height), 10, 10)];
label.text = page;
label.textAlignment = NSTextAlignmentCenter;
label.layer.shadowOffset = CGSizeMake(0, 2);
label.layer.shadowRadius = 2;
label.layer.shadowOpacity = 0.3;
label.layer.shadowPath = [UIBezierPath bezierPathWithRect:label.bounds].CGPath;
label.clipsToBounds = NO;
[contentView addSubview:label];
}
Constraining the scroll view's contentOffset
As the user moves his finger around, I want to prevent the scroll view from showing an area of its content that doesn't contain a page. Whenever the scroll view scrolls (by updating its contentOffset), it sends scrollViewDidScroll: to its delegate, so I can implement scrollViewDidScroll: to reset the contentOffset if it goes out of bounds:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGPoint contentOffset = scrollView_.contentOffset;
First, I want to constrain contentOffset so the user can only scroll horizontally or vertically, not diagonally:
CGPoint constrainedContentOffset = [self contentOffsetByConstrainingMovementToOneDimension:contentOffset];
Next, I want to constrain contentOffset so that it only shows parts of the scroll view that contain pages:
constrainedContentOffset = [self contentOffsetByConstrainingToAccessiblePoint:constrainedContentOffset];
If my constraints modified contentOffset, I need to tell the scroll view about it:
if (!CGPointEqualToPoint(contentOffset, constrainedContentOffset)) {
scrollView_.contentOffset = constrainedContentOffset;
}
Finally, I update my idea of the current map position based on the (constrained) contentOffset:
mapPosition_ = [self mapPositionForContentOffset:constrainedContentOffset];
}
Here's how I compute the map position for a given contentOffset:
- (MapPosition)mapPositionForContentOffset:(CGPoint)contentOffset {
return (MapPosition){ roundf(contentOffset.x / kPageSize.width),
roundf(contentOffset.y / kPageSize.height) };
}
Here's how I constrain the movement to just horizontal or vertical and prevent diagonal movement:
- (CGPoint)contentOffsetByConstrainingMovementToOneDimension:(CGPoint)contentOffset {
CGPoint baseContentOffset = [self contentOffsetForCurrentMapPosition];
CGFloat dx = contentOffset.x - baseContentOffset.x;
CGFloat dy = contentOffset.y - baseContentOffset.y;
if (fabsf(dx) < fabsf(dy)) {
contentOffset.x = baseContentOffset.x;
} else {
contentOffset.y = baseContentOffset.y;
}
return contentOffset;
}
Here's how I constrain contentOffset to only go where there are pages:
- (CGPoint)contentOffsetByConstrainingToAccessiblePoint:(CGPoint)contentOffset {
return [self isAccessiblePoint:contentOffset]
? contentOffset
: [self contentOffsetForCurrentMapPosition];
}
Deciding whether a point is accessible turns out to be the tricky bit. It's not enough to just round the point's coordinates to the nearest potential page center and see if that rounded point represents an actual page. That would, for example, let the user drag left/scroll right from page 1, revealing the empty space between pages 1 and 2, until page 1 is half off the screen. We need to round the point down and up to potential page centers, and see if both rounded points represent valid pages. Here's how:
- (BOOL)isAccessiblePoint:(CGPoint)point {
CGFloat x = point.x / kPageSize.width;
CGFloat y = point.y / kPageSize.height;
return [self isAccessibleMapPosition:(MapPosition){ floorf(x), floorf(y) }]
&& [self isAccessibleMapPosition:(MapPosition){ ceilf(x), ceilf(y) }];
}
Checking whether a map position is accessible means checking that it's in the bounds of the grid and that there's actually a page at that position:
- (BOOL)isAccessibleMapPosition:(MapPosition)p {
if (p.y < 0 || p.y >= map_.count)
return NO;
NSArray *mapRow = map_[p.y];
if (p.x < 0 || p.x >= mapRow.count)
return NO;
return ![mapRow[p.x] isKindOfClass:[NSNull class]];
}
Forcing the scroll view to rest at page boundaries
If you don't need to force the scroll view to rest at page boundaries, you can skip the rest of this. Everything I described above will work without the rest of this.
I tried setting pagingEnabled on the scroll view to force it to come to rest at page boundaries, but it didn't work reliably, so I have to enforce it by implementing more delegate methods.
We'll need a couple of utility functions. The first function just takes a CGFloat and returns 1 if it's positive and -1 otherwise:
static int sign(CGFloat value) {
return value > 0 ? 1 : -1;
}
The second function takes a velocity. It returns 0 if the absolute value of the velocity is below a threshold. Otherwise, it returns the sign of the velocity:
static int directionForVelocity(CGFloat velocity) {
static const CGFloat kVelocityThreshold = 0.1;
return fabsf(velocity) < kVelocityThreshold ? 0 : sign(velocity);
}
Now I can implement one of the delegate methods that the scroll view calls when the user stops dragging. In this method, I set the targetContentOffset of the scroll view to the nearest page boundary in the direction that the user was scrolling:
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
if (fabsf(velocity.x) > fabsf(velocity.y)) {
*targetContentOffset = [self contentOffsetForPageInHorizontalDirection:directionForVelocity(velocity.x)];
} else {
*targetContentOffset = [self contentOffsetForPageInVerticalDirection:directionForVelocity(velocity.y)];
}
}
Here's how I find the nearest page boundary in a horizontal direction. It relies on the isAccessibleMapPosition: method, which I already defined earlier for use by scrollViewDidScroll::
- (CGPoint)contentOffsetForPageInHorizontalDirection:(int)direction {
MapPosition newPosition = (MapPosition){ mapPosition_.x + direction, mapPosition_.y };
return [self isAccessibleMapPosition:newPosition] ? [self contentOffsetForMapPosition:newPosition] : [self contentOffsetForCurrentMapPosition];
}
And here's how I find the nearest page boundary in a vertical direction:
- (CGPoint)contentOffsetForPageInVerticalDirection:(int)direction {
MapPosition newPosition = (MapPosition){ mapPosition_.x, mapPosition_.y + direction };
return [self isAccessibleMapPosition:newPosition] ? [self contentOffsetForMapPosition:newPosition] : [self contentOffsetForCurrentMapPosition];
}
I discovered in testing that setting targetContentOffset did not reliably force the scroll view to come to rest on a page boundary. For example, in the iOS 5 simulator, I could drag right/scroll left from page 5, stopping halfway to page 4, and even though I was setting targetContentOffset to page 4's boundary, the scroll view would just stop scrolling with the 4/5 boundary in the middle of the screen.
To work around this bug, we have to implement two more UIScrollViewDelegate methods. This one is called when the touch ends:
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
if (!decelerate) {
[scrollView_ setContentOffset:[self contentOffsetForCurrentMapPosition] animated:YES];
}
}
And this one is called when the scroll view stops decelerating:
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
CGPoint goodContentOffset = [self contentOffsetForCurrentMapPosition];
if (!CGPointEqualToPoint(scrollView_.contentOffset, goodContentOffset)) {
[scrollView_ setContentOffset:goodContentOffset animated:YES];
}
}
The End
As I said at the beginning, you can download my test implementation from my github repository and try it out for yourself.
That's all, folks!
I'm assuming you're using the UIScrollView in paged mode (swipe to show an entire new screen).
With a bit jiggery-pokery you can achieve the effect you want.
The trick is to ensure that whatever square you're currently viewing, you have the UIScrollView configured so that only the visible central view, and the surrounding view that you could scroll too, are added to the scroll view (and at the correct offset). You also must ensure that the size of the scrollable content (and the current offset) is set correctly, to prevent scrolling in a direction that would take you to no content.
Example: suppose you're viewing square 6 currently. At that point, your scroll view would just have 4 views added to it: 4, 5, 6 and 7, in the correct relative offsets. And you set the content size of the scroll view to be equivelant to 2 x 2 squares size. This will prevent scrolling down or to the left (where there are no tiles) but will allow scrolling in the correct direction.
You'll need your delegate to detect scrollViewDidEndDecelerating:. In that instance, you then have to set up your views, content offset, and content size as described above, for the new location.
I added a -(void) detectTouch: (UIPanGestureRecognizer *) event for UIScrollView and detecting the angle on which user is moving his finger. My task is to scroll the UIScrollView horizontally only when user is moving the finger between 0 - 30 degrees (just to make sure he is drawing a horizontal straight line) otherwise I have to disable the UIScrollView scroll.
I am detecting the angle by drawing a triangle using the touch starting point and ending point.
Problem: I enabled the UIScrollView scroll when the angle is < 30 degrees but this is not working on the first time. Although I enabled scroll using scrollEnabled = YES it is working only when user is stopped touching the screen (taking the finger from the screen).
The following code I used to
- (void)viewDidLoad
{
[super viewDidLoad];
[self PanGesture:self.view callBack:#selector(detectTouch:) delegate:self];
incrementer = 0;
}
-(void) detectTouch: (UIPanGestureRecognizer *) event{
// Calculating point A on gesture starts
if(event.state == UIGestureRecognizerStateBegan){
pointA.x = fabs([event translationInView:event.view].x);
pointA.y = fabs([event translationInView:event.view].y);
NSLog(#"A: %f, %f", pointA.x, pointA.y);
}
incrementer += 1;
// Start calculating Point B, Point C on calling this function 3 times
if(incrementer >= 3){
// Calculating point C
pointC.x = fabs([event translationInView:event.view].x);
pointC.y = fabs([event translationInView:event.view].y);
NSLog(#"C: %f, %f", pointC.x, pointC.y);
// calculate pointB using A, C
pointB.x = fabs(pointC.x);
pointB.y = fabs(pointA.y);
NSLog(#"B: %f, %f", pointB.x, pointB.y);
float X = pointB.x - pointA.x;
float Y = pointC.y - pointB.y;
float angle = (atan(fabs(Y) / fabs(X)) * 180 / M_PI);
if(angle > 30){
// This disable is not working on while user is moving the finger
self.myScrollView.scrollEnabled = NO;
NSLog(#"UIScroll Disabled");
}else{
// This enable is not working on while user is moving the finger
self.myScrollView.scrollEnabled = YES;
NSLog(#"UIScroll Enabled");
}
incrementer = 0;
}
}
How can I enable UIScrollView scroll while user is moving the touch?
Since UIScrollView seems to accept scrolling only with a new touch after you set .scrollEnabled to YES, I would do the following:
set .scrollEnabled to NO
Track the touch (e. g. with touchesMoved::)
check whether you 30 degrees condition is met
use the movement to adjust UIScrollView.contentOffset
I have a UIView that I rotate with this code:
helpView.transform = CGAffineTransformMakeRotation(degreesToRadians( rotationAngle ));
Where degreeToRadians just is a macro to convert from degrees to radians.
This works fine as long as the view is visible, eg alpha = 1. When I hide it (alpha = 0, which I animate) it does not rotate any more. I guess this is a smart way for the devices to "save" on drawing time, but is there any way I can force it to be drawn even when alpha is 0? Otherwise I will have to rotate it before I show it again.
Any good ideas?
Thanks
Edit: This is the code I use to show/hide the view.
-(void)showHelp
{
bool helpAlpha = !helpView.alpha;
CGFloat newScale;
if (helpView.alpha) {
newScale = kHelpSmall;
helpView.transform = CGAffineTransformMakeScale(kHelpBig, kHelpBig);
} else {
newScale = kHelpBig;
helpView.transform = CGAffineTransformMakeScale(kHelpSmall, kHelpSmall);
}
[UIView animateWithDuration:(kAnimationTimeShort / 2) animations:^(void) {
[helpView setAlpha:helpAlpha];
helpView.transform = CGAffineTransformMakeScale(newScale, newScale);
}];
}
As you see I also scale it for a nicer effect. Works perfect when visible, does not rotate when alpha = 0. Rotation is done in another method, where I would prefer to keep it as I also rotate some other views there.
You are resetting the transform every time you use CGAffineTransformMake*. If you do this, you will get either a rotated transform or a scaled one. I am assuming the scaled one is after the rotated one and hence you aren't able to see the view rotated. If you need both the effects to remain, you will have to use CGAffineTransformRotate. So a scale and rotate will be
helpView.transform = CGAffineTransformMakeScale(kHelpSmall, kHelpSmall);
helpView.transform = CGAffineTransformRotate(helpView.transform, degreesToRadians(rotationAngle));
The order might vary.